1. Field of the Invention
The present invention relates to a point emission type light emitting element having a light emitting area restricted within a tiny region, and to a concentrating point emission type light emitting element that concentrates light emitted thereby and outputs the light through a tiny region.
2. Description of the Related Art
The present applicant already developed nitride semiconductor light emitting diodes that emit blue and green light with high output power and are used in practical applications as light sources for large image display apparatuses. The nitride semiconductor light emitting element is manufactured, for example, by forming p-type and n-type ohmic electrodes on a multi-layer semiconductor film that is formed from a nitride semiconductor of GaN, AlN, InN or a mixed crystal thereof on a sapphire substrate, and separating the elements into chips by such processes as cleaving, RIE etching or dicing. The light emitting element made as described above emits light not only from a light emitting layer but also from cut-off surfaces and principal plane of the substrate after causing the light to repeat transmission through the other semiconductor layers and in the substrate, refraction and reflection therein.
In recent years, there have been increasing demands for light emitting elements that restrict the light emitting area within a microscopic region for such applications as the light sources for optical communication, electrophotography and virtual reality display. To meet these demands, nitride semiconductor light emitting elements of various constitutions have been proposed with the light emitting area restricted within a microscopic region.
An end face emitting type light emitting element has been proposed as a light emitting element having microscopic light source. The end face emission light emitting element employs double heterojunction structure wherein a light emitting layer is sandwiched by forming p-type and n-type semiconductor layers that have wide band gap, as the basic structure similarly to a semiconductor laser. For example, an end face emission type light emitting diode made of nitride semiconductor employs separation-confinement heterojunction structure (SCH) based on AlGaN/GaN/InGaN.
However, in the constitution of the proposed light emitting element that restricts the light emitting area within a microscopic region, a high accuracy of patterning is required to restrict the light emitting area within the microscopic region, and an advanced photolithography technology must be used. This results in the problem that the light emitting element that restricts the light emitting area within the microscopic region cannot be provided at an economical price.
Although the end face emission type light emitting diode can be made with small spot size, multi-mode light emission is produced since light is emitted not only from the end face of the light emitting layer but also from the end faces of the n-type semiconductor layer formed nearer to the substrate than the light emitting layer, thus making it unsuitable for such applications as a single spot of good near-field pattern is required.